First Year Physics Undergrad Recap

18.07.2021//

How to reuse old rational mechanics notes:

Pick your old notes

Enjoy destroying them

Drown them in the water and blend

Make your own frame with woods and a mosquito net 🦟

Use the frame to make perfect sheets

Wait 73839393 hours

When they are dried be careful and don’t rip them off

Write down your personal theory of everything

Win the Nobel

Use the remaining recycled paper to dry your happy tears

15.04.22// Experimental physics is killing me. And Latex always messes with my head, ft. my very messy lab journal.

Vera Rubin

Vera Florence Cooper Rubin was an American astronomer who pioneered work on galaxy rotation rates. She uncovered the discrepancy between the predicted angular motion of galaxies and the observed motion, by studying galactic rotation curves. This phenomenon became known as the galaxy rotation problem, and was evidence of the existence of dark matter. Although initially met with skepticism, Rubin’s results were confirmed over subsequent decades. Her legacy was described by The New York Times as “ushering in a Copernican-scale change” in cosmological theory.

Rubin spent her life advocating for women in science and was known for her mentorship of aspiring women astronomers. Her data provided some of the first evidence for dark matter, which had been theorized by Fritz Zwicky in the 1930s. She was honored throughout her career for her achievements, and received the Bruce Medal, the Gold Medal of the Royal Astronomical Society, and the National Medal of Science, among others. source

Astrophysicists detect first black hole-neutron star mergers

A long time ago, in two galaxies about 900 million light-years away, two black holes each gobbled up their neutron star companions, triggering gravitational waves that finally hit Earth in January 2020.

Discovered by an international team of astrophysicists including Northwestern University researchers, two events—detected just 10 days apart—mark the first-ever detection of a black hole merging with a neutron star. The findings will enable researchers to draw the first conclusions about the origins of these rare binary systems and how often they merge.

“Gravitational waves have allowed us to detect collisions of pairs of black holes and pairs of neutron stars, but the mixed collision of a black hole with a neutron star has been the elusive missing piece of the family picture of compact object mergers,” said Chase Kimball, a Northwestern graduate student who co-authored the study. “Completing this picture is crucial to constraining the host of astrophysical models of compact object formation and binary evolution. Inherent to these models are their predictions of the rates that black holes and neutron stars merge amongst themselves. With these detections, we finally have measurements of the merger rates across all three categories of compact binary mergers.”

The research will be published June 29 in the Astrophysical Journal Letters. The team includes researchers from the LIGO Scientific Collaboration (LSC), the Virgo Collaboration and the Kamioka Gravitational Wave Detector (KAGRA) project. An LSC member, Kimball led calculations of the merger rate estimates and how they fit into predictions from the various formation channels of neutron stars and black holes. He also contributed to discussions about the astrophysical implications of the discovery.

Kimball is co-advised by Vicky Kalogera, the principal investigator of Northwestern’s LSC group, director of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and the Daniel I. Linzer Distinguished Professor of Physics and Astronomy in the Weinberg Colleges of Arts and Sciences; and by Christopher Berry, an LSC member and the CIERA Board of Visitors Research Professor at Northwestern as well as a lecturer at the Institute for Gravitational Research at the University of Glasgow. Other Northwestern co-authors include Maya Fishbach, a NASA Einstein Postdoctoral Fellow and LSC member.

Two events in ten days

The team observed the two new gravitational-wave events—dubbed GW200105 and GW200115—on Jan. 5, 2020, and Jan. 15, 2020, during the second half of the LIGO and Virgo detectors third observing run, called O3b.

Although multiple observatories carried out several follow-up observations, none observed light from either event, consistent with the measured masses and distances.

“Following the tantalizing discovery, announced in June 2020, of a black-hole merger with a mystery object, which may be the most massive neutron star known, it is exciting also to have the detection of clearly identified mixed mergers, as predicted by our theoretical models for decades now,” Kalogera said. “Quantitatively matching the rate constraints and properties for all three population types will be a powerful way to answer the foundational questions of origins.”

All three large detectors (both LIGO instruments and the Virgo instrument) detected GW200115, which resulted from the merger of a 6-solar mass black hole with a 1.5-solar mass neutron star, roughly 1 billion light-years from Earth. With observations of the three widely separated detectors on Earth, the direction to the waves’ origin can be determined to a part of the sky equivalent to the area covered by 2,900 full moons.

Just 10 days earlier, LIGO detected a strong signal from GW200105, using just one detector while the other was temporarily offline. While Virgo also was observing, the signal was too quiet in its data for Virgo to help detect it. From the gravitational waves, the astronomers inferred that the signal was caused by a 9-solar mass black hole colliding with a 1.9-solar mass compact object, which they ultimately concluded was a neutron star. This merger happened at a distance of about 900 million light-years from Earth.

Because the signal was strong in only one detector, the astronomers could not precisely determine the direction of the waves’ origin. Although the signal was too quiet for Virgo to confirm its detection, its data did help narrow down the source’s potential location to about 17% of the entire sky, which is equivalent to the area covered by 34,000 full moons.

Where do they come from?

Because the two events are the first confident observations of gravitational waves from black holes merging with neutron stars, the researchers now can estimate how often such events happen in the universe. Although not all events are detectable, the researchers expect roughly one such merger per month happens within a distance of one billion light-years.

While it is unclear where these binary systems form, astronomers identified three likely cosmic origins: stellar binary systems, dense stellar environments including young star clusters, and the centers of galaxies.

The team is currently preparing the detectors for a fourth observation run, to begin in summer 2022.

“We’ve now seen the first examples of black holes merging with neutron stars, so we know that they’re out there,” Fishbach said. “But there’s still so much we don’t know about neutron stars and black holes—how small or big they can get, how fast they can spin, how they pair off into merger partners. With future gravitational wave data, we will have the statistics to answer these questions, and ultimately learn how the most extreme objects in our universe are made.”

Art by Simone Ferriero

31/01/22

100 days of productivity: 31/100

happy lunar new year!!! 🧧🧧🧧

6 semesters of physics - recap of the B.Sc. degree

Finally! I've finished my Bachelor's degree in Physics! Because it has been a while since I gave a recap about my studies, I guess now is a good moment to share some of my experiences and give you some impressions - whatever you're doing, whether you want to start studying physics or whether you're already struggling through your studies.

Not surprisingly, studying physics is indeed tedious business. Most often one works (at least I did, and many of my fellow students had a similar schedule) every day of the week. During the semester there's simply not a lot of time for loads of recreational time - but: It gets better. There's not more free time in the higher semesters, but one has less self doubts and the frustration one feels in the first semesters evolves into a form of motivation. It becomes normal to spend hours staring on exercise sheets or trying to understand a certain concept - contemplation of this kind becomes a kind of joy, but to be honest, a fraction of frustration remains of course. At least as I experienced it, the studies become less exhausting the more exams one has already passed. Simultaneously, one gains further motivation because the more sophisticated the topics are the more stimulating the studies are.

Now, some hints and insights that - at least I think so - helped me to get through the studies in a decent time (by not exceeding the standard period of study) and staying motivated (besides the hints I've pointed out here):

Keep up the amount of work you do for your studies: Try not to rest on your laurels once you've completed your first semesters. Keep on studying - there is so much to learn, the first semesters are only the beginning!

Dont hesitate to repeat topics from the first semesters. It is normal to forget and furthermore it is normal to understand things just a couple of semesters later after facing them the first time. Sometimes it feels redundant to do a recap on e.g. linear algebra - but redundance, to some extent, helps to gain deeper understanding.

The feeling that you actually understand nothing will remain - always, I'm afraid. This might sound disillusioning but it is simply true. The more you learn and understand the more you see what you haven't understood yet or not even know about. Taking undergrad lectures is always focused on the basics of each theory - I guess it is normal to feel lost sometimes, even if you've studied for three years already. During the undergrad studies one can merely learn superficially - deeper understanding in a chosen area of physics will (hopefully) follow in the postgraduate studies.

Use your vacations to read about topics that might interest you beyond the lectures. I know that this sounds insane, in particular because recreational time is rare. But there are always some topics that are mentioned in the lectures and merely browsed superficially. Additionally, although the standard lectures are most often demanding enough, they are not always the main source of motivation. It is worth it to pick some of these topics and do some reading in your free time after the exams. At least for me this was a way to find topics that made me say: "Yes, this is exactly why I am studying physics". That way I stumbled across foundations of quantum mechanics, i.e. the realm of Bell's Theorem, interpretations and alternative theories of QM. It is very stimulating to find a branch of physics which simply fascinates you - I guess one cannot find them in the standard lectures: You have to search for the topics which please you the most. Doing so adds momentum to your motivation.

Do not exclude physics from your free time. Of course it is crucial to have physics-free hours but I think - psychologically - it is essential to draw joy out of your studies and not seeing it merely as an obligation. In case you regard any physics just as work and not as joy, then you run into danger losing your motivation on the long road.

Study responsibly. Sleep enough, eat healthy (vegan) and drink sufficient amounts of water - Although it is difficult sometimes, do not let bad habits overwhelm you. Additionally, also find joy beyond physics and allow yourself to do hobbies, i.e. drawing, reading on politics/literature/whatever, watching movies. At least in such a range that you will not merely become a narrow-minded scientist.

So, these were some points which came to my mind, hopefully they will help at least some of you! Do you have further/better hints to share? Post them below 👇👇👇

Hurrah! Done with this! The best book I've ever come across ❤

Radio Astronomy

So I learnt something really cool today. Radio astronomy. Radio astronomy is done at ~ 1.4 GHz frequency. WHY YOU ASK??? Because hydrogen is the most abundant element in the universe!!! And hydrogen atoms have one electron !! Electrons possess spins!! Spins can flip!! And when they do, they emit a wavelength of 21 cm!! Which corresponds to a frequency of 1.4 GHz (f = c/λ). And since hydrogen is basically EVERYWHERE, they use that to observe celestial bodies and it is a very protected frequency which means radio stations, satellites and cellphone towers can't use it!!